I just lost another igniter (second one in three years), and I'm ready to try something different. I've read Paul Yaw's recommendations for simultaneous direct fire to the leading coils using an MSD 6A box excited by the magnetic pickup at the base of the distributor to fire two leading coils in a wasted spark arrangement, however his setup retained the OEM trailing coil ignition.

I've been wondering if it would be possible to run direct fire for the trailing coils, too. I'd like to run an FC crank angle sensor instead of my '84 distributor. I'd use the leading signal to direct fire the leading plugs via Yaw's setup. For the trailing side, I'd use one MSD 6A and one coil for each trailing plug. Will the signal out of the crank angle sensor allow me to distribute one trailing signal from the other? Will this setup work? Is there a better way to setup direct fire?

 

the CAS uses the ECU to work it, so you would have to wire that up not really worth it. You can get a second gen leading coil and run it for the trailing only. You do not want to do a direct fire on both trailing and leading it will run very badly. It will be like a one rotor car. It is very simple to do this mod.. you need another ignitor and some heat sink compound, because the crap that is on the back of the ignitor by now is worn off.

 

You're thinking with pistons on the brain. Before you get upset, let me explain. Piston engines need all the spark they can get to each plug. That's logical. I'm sure you're like Duh! A rotary does too, but trailing can remain stock on an FB with only a slight change in plug wire position on the cap (from trailing to leading to use the carbon button and only one gap to jump).

How much are you willing to spend anyway? How much power do you think trailing actually adds to your engine?

Save your money and don't upgrade trailing; it's simply not worth the effort.

As for leading, all you need is one more ignitor and one more coil. You'll end up with two leading ignitors and two leading coils, triggered by the leading pickup. Trailing, of course, remains stock (other than the cap wire positions).

Yes, it does work and is extremely cheap. You can pickup an extra ignitor on ebay right now. http://cgi.ebay.com/ebaymotors/ws/eB...tem=2469853919

I'm sure a stock FB coil could be had for less than half the price of one of those MSD coils.

Of course if you're bent on getting an MSD, you might as well spring a couple more bucks on the 6AL and also get yourself one stock FC leading coil. The FC leading coil is a 'DIS' coil and has one input (primary) and two outputs (secondary) for both leading spark plugs. The theory suggests this actually works better than Paul's two coil idea because of the nature of the CD output of the MSD. You see, the MSD is converting 12V with high amperage to 350V low amperage very quickly, and then treats the coil like a step-up transformer. This is fine if you've got one coil that's been manufactured with CDI in mind. However, if you've got two coils hooked to the MSD in parallel (as per Yaw), this chops the already low amperage in half. Also, if the coil was originally intended for the typical transistor ignition, like the FB came stock with (Kettering, in other words), it could overheat and burn out in a short time.

Anyway, if you've made up your mind to get an MSD, please also get a DIS coil intended for CDI. Otherwise, save a boat load of money and get excellent results with DLIDFIS. I've tried them both and prefere DLIDFIS' long duration kettering spark over the MSD's short duration at-pretty-much-anything-above-idle spark. I still have my MSD though, and I even recently picked up an FC leading coil. I'll try the MSD again, this time with a better designed SINGLE primary coil instead of the clunky two-coils-in-parallel sillyness of yore.

 

The link you gave for DLIDFIS bummed out in yahoo. Do you have an alternate link?

B

 

from Paul Yaws web site:

"The ignition system on a rotary, or any other engine for that matter, cannot be ignored when performing horsepower mods. If you are still using a distributor, you are losing horsepower. Period! If you have a second or third generation RX-7, you already have an excellent ignition system. These systems are direct fire, with a "wasted spark" setup on the leading Ignition. Direct fire ignition systems deliver a hotter spark, and the timing is much more stable. As an added benefit, you don't have to change your cap and rotor every other week to keep you car running well.
These direct fire systems are very good, but still leave room for improvement. The biggest problem is that the bean counters at Mazda, and all other auto manufacturers have more to do with the finished product than the engineers do. In other words, make it as cheap as possible. These distributorless systems are known as an inductive discharge ignition. Inductive discharge ignitions suffer from poor spark at high rpm, and this is aggravated by the wasted spark arrangement on the leading ignition which fires twice per revolution. Without going into a lot of detail, the simplest explanation is that the coils do not have enough time to build a strong magnetic field at high rpm, and so the spark continues to weaken as the engine speed increases. The bean counters don't give a ****, because this system works great at low speed, and gives good mileage and driveability. This is the number one priority, even in a sports car.

Buy an MSD 6A

Luckily, this is easy to fix. Buy an MSD. In case you didn't hear me the first time, Buy an MSD! Every vehicle on the planet should have one, even your grandmothers grocery getter. The MSD is a capacitive discharge system, which does not loose spark intensity at high rpm. Capacitive discharge systems deliver a very strong, but short duration spark. To overcome this, the MSD delivers multiple sparks over twenty degrees of eccentric shaft duration. This amounts to as many as six sparks at idle, and as little as two at high rpm, but no matter how many times it fires, the spark always lasts for a full twenty degrees. This is the best of both worlds, a high intensity, long duration spark. Just about every racecar on the planet has one, and you should too.
I have installed many MSD's, and the results were always more power, better driveability, and better gas mileage. A second or third gen. will require three boxes for the entire ignition system. This is quite expensive. You can make a large improvement by simply buying one box for the leading, and the results will be even better if you replace the stock dual coil with two MSD Blaster coils. Simply run both coils from the same MSD box. The ultimate setup is of course three MSD 6A's, and four blaster coils, but this will set you back about $700, and you probably will not fit all of this under the hood.
Well, that's about it for the second and third gen RX's. I am currently testing spark plugs, and I will post the results in the future. There is more power here than I thought, especially after I got away from the conventional NGK's. As soon as I have some dyno results, they will be on the page.

Distributors Suck

Now for the first generation. Distributors suck! Distributors require that the charge jump a .075" gap from the rotor to the cap before it can even fire the .055" gap of the spark plug. The gap in the distributor cap is easier to fire than the spark plug gap, because there is much less pressure, but it is still a really shitty way to make fire. Luckily it is relatively easy to convert the leading ignition to direct fire. I finally got around to doing this on my 13B, and then I was mad at myself for not doing it sooner.
Before the conversion, I was using an MSD 6A, with an Accele super coil. This is a lot of juice, so I was really surprised at the improvement after converting to direct fire. I called MSD to be sure that their box would fire two coils, and their tech guy said "Hell, it would probably fire a whole row of coils." I set it up with two stock coils for the leading ignition and was stunned at the results. The engine made more power everywhere in the powerband, and the driveabilty improved dramatically. I will never again run an MSD through the distributor.
Here's how it works. All you need is an MSD 6A, and an extra coil. Two for the leading, and one for the trailing. Trigger the MSD with the magnetic trigger inside of the distributor.Do not try to trigger the MSD with the ignitor! The ignitor output is very "dirty", and does not give the MSD a clean signal to work with. Simply cut the green, and red wires that go from the leading magnetic trigger to the ignitor. The leading ignitor is the one facing the front of the vehicle. Connect the green wire from the trigger, to the purple wire of the MSD, and connect the red wire from the trigger, to the green wire of the MSD. Wire power, ground, and ignition as per MSD's instructions. The orange, and black 16ga. wires from the MSD go to the coil. In this case, make two jumpers and connect both coils to these wires. Make sure that the polarity is correct. The stock coils are labeled positive and negative. The orange wire goes to positive, the black wire goes to negative. Do not screw this up! The same goes for the magnetic trigger in the distributor. If you wire the trigger backwards, the timing will be advanced by approximately thirty degrees. Now simply run a plug wire from each coil to a leading spark plug. It doesn't matter which one, because they will both fire at the same time. Leave the trailing ignition just as it is.
This is referred to as a "wasted spark" system because eack rotor recieves an additional spark during the exhaust phase. On a rotary, this extra spark is actually beneficial, because it fires at the trailing end of the chamber which is where most of the unburned fuel is concentrated. Igniting this fuel will not make more power, but it will clean up the emissions slightly. DO NOT try this setup on the trailing ignition. Because of the different spark plug location you will ignite the incoming mixture from the next stroke. At best, you will lose power, at worst, you will break apex seals. If you have any questions about this, feel free to send a message. This is a simple wiring job, and the results are amazing. This is cheap power, and the improvement in gas mileage will probably pay for the MSD in a years time. I have not tried this with upgraded coils, but when I do, I will let you know if there is further improvement. I am only sorry that I didn't try this on the dyno so that I could measure the improvement in horsepower. Next time I have a 12A on the dyno, I might do a comparison, and post the results.

Spark Plugs

I have been doing some spark plug testing recently, and have been surprised at the results. I have been doing this testing on my daily driver, a bridge ported 13B. Almost everything starts here, and then makes its way to the dyno if the results seem worthwhile. In this engine, I have had the best luck with the Autolite 2526. You know, those cheap nasty plugs that they try to sell you at the discount auto parts store. These plugs have only one ground strap, instead of four like the NGK, or ND plugs. If you look at one of these, it makes sense that they would produce more power because the spark is much less shrouded. This will allow the flame to travel more easily from the face of the plug to the combustion chamber which is a big problem with the rotary anyway.
I should mention that these plugs do not work well without an MSD. It seems that the gap is to great for the stock ignition system to fire consistently. I found that with an MSD on the leading, and stock ignitor on the trailing, that these worked better in the trailing position than the NGK's. However,a friend with a completely stock ignition found that they just plain didn't work as well as the NGK. Until I have a chance to check this out myself, I will not reccommend them for stock ignitions.
After trying every plug made for the rotary, and finding that the cheap Autolite worked best, I decided to call Autolite and find out why. This plug was only available in one heat range, and so I at least wanted to know if they had something similar in a hotter and cooler plug. I was very lucky to contact Don Ward who is an engineer in charge of their motorsports program. I explained all of this to Don, and he agreed that the spark was less shrouded, and this is why they made more power. He also expalined that a resistor plug was prone to misfire above about 7000 rpm. I didn't know this, and so I expalined to him that I was stupid, and asked what he recommended. Autolite makes an extended tip non resistor plug that is available in four heat ranges, and costs a whopping 99 cents. The extended tip helps to further unshroud the spark, and also moves the electrode .060" closer to the rotor housing surface. This is a conventional style plug, with the ground strap reaching all of the way over the top of the electrode. I ground this off to convert it to a side fire, set the gap to .055", and headed out to the truck to install them. Oops, they didn't fit! This plug has a very short shell, and so the socket needs to extend not only beyond the boss on the rotor housing, but beyond the flat surface as well. Have die grinder will travel! Twenty minutes later, I had the plugs installed in the leading position and Holy ****! I never thought that a spark plug could make such a difference. Power improved throughout the rpm range, and it was much smoother at high rpm.
These will definetely be tested on the dyno, and I promise to post the results so that you can see it for yourself. The next step is to replace the sealing washer with a thinner piece to get the spark an additional .040" closer to the combustion chamber. I will try this on the street engine as well, and these plugs will be comparison tested on the E-Production engine which will be on the dyno the last week of October.

Spark Plug Update 11/3

Well, I recieved some new plugs from Autolite. This is a plug that was developed for Nascar Winston Cup racing on the superpeedways. It just happens to fit the rotaries. It is a 5/8 hex, and so it will fit without modifications. The plugs that I recieved (part number 3910) are prototype pieces, and I am still not sure if they will be production pieces.
These plugs were designed to withstand hundreds of full throttle laps. They are an extended tip design, but they look very much like the BUR-EQ's. They have four ground straps, that are part of the shell, rather than being welded to the shell. So, to get down to details, they extend so far into the rotor housing that the center electrode is only .030" from the apex seal. If you were to install these without the sealing washers, they would protrude into the chamber and munch your apex seals. For the sake of comparison, they are nearly .100" longer than a stock plug.
So how do they perform? Not as well as the modified 99 cent plugs. They do however perform better than the stock plugs, and they will withstand just about anything that a race motor could do to them. But this is not the end of the story. I milled off three of the ground straps, and reinstalled them. Once again unshrouding the spark paid off. The difference was amazing! They work GREAT! So far better than anything I have tried. Autolite says that these plugs will be expensive. Probably in the 5 to 8 dollar range, if they are even produced at all. If these are not produced, it will not have been a waste of time, because they helped illustrate the importance of unshrouding the spark.
As an alternative, I am searching the manufacturers catalogs for a non resistor, 5/8" hex, extended tip plug that will reach as far into the housing as these do. If I can find something in the appropriate heat range, it should work every bit as well, as the testing seems to indicate that there are only two important factors. 1. Getting the spark as close as possible to the chamber. 2. Keeping the spark as unshrouded as possible. If I can find something with a 5/8" hex, they will fit without grinding, or investing in a $50 spark plug socket.

ANOTHER Spark Plug Update 12/4

Well I finally found what I was looking for. Champion makes an extended tip non resistor plug with a 5/8" hex. It is available in four heat ranges. These plugs have the same configuration and dimensions as the Autolite 51's. So far I have been very disappointed with the life span of the Autolites. I was reminded by a friend that at 99 cents a piece it doesn't really matter, but there has got to be something that works, and lasts longer. The Champion plugs cost about $2.50 each, and the part numbers are C57YC, C59YC, C61YC, and C63YC. The heat range is equivalent to an NGK 7, 8, 9, and 10 respectively. They do require trimming of the ground strap just like the Autolites, and after closer inspection I realized that after trimming they do fit in the trailing position. I have not been driving my truck for the last month, so I cannot yet say how the power is, but being the same configuration as the Autolites I would imagine that they work as well. As for life expectancy, I don't know that yet either. So why am I telling you this? So that you will try them yourself, and give me some feedback. I will compare these to all the others on the dyno, and post the results, but this could be a month or more away.
I will eventually figure out what works best, and how long they last compared to the stock plugs, but I do have to pay the bills. In the meantime, I would really appreciate feedback from any of you who wish to experiment with these plugs. When I finally decide on a particular plug I will post the dyno results, so that you can see the results for yourself. When this is all finalized you will all be able to go a little bit faster for pocket change.

ANOTHER Spark Plug Update 6-22

OK, here we go again. As I mentioned before, the Autolite didn't last long. The Champions were even worse, and turned out to be quite fragile. I finally scrounged an NGK Sportline Catalog from a local motorcycle shop, and guess what I found. A 14mm., .750 reach, extended tip plug. BP-ES Pay dirt! Same design and dimensions as the Autolite and Champion extended tip plug. After performing the same modifications I installed them, and beat them to death. They are very tough. Just to be sure, I installed a BP7ES in the leading position which is a bit hot for an extended tip plug. I have driven around with these 7's installed for nearly a month now, and even gave them the torture test by running 90mph on the freeway for several miles. This is normally no big deal, but since the plug is too hot for this application it really put them to the test. After this I examined the ceramic with a magnifying glass, and could see no signs of cracking. The performance is the same as the other extended tip plugs, but they are much more durable. They are available at most motorcycle shops in two different heat ranges. BP7ES, and BP8ES. A BP9ES is also available, but the local shops do not stock it. They can be ordered however. The only downside is that they are a 13/16 short shell plug, and you will need a Racing Beat spark plug socket to install them. NGK also makes a racing version of this plug available in heat ranges 7,8,9, and 10 They are a 5/8 hex, so no special socket is required. The part number is R5400-heat range number. They have a fine wire gold palladium center electrode, which will reduce the voltage required to jump the gap. This may be helpful if they are used with a distributor, and stock ignitors. These are "race" plugs, and are quite pricey. Do not forget that these plugs must be converted to side fire configuration or they will protrude into the combustion chamber and break your apex seals. I will probably purchase a case of each, and cut the ground straps on the mill. I do not yet know what the pricing will be. Next months technical article will discuss the ignition system, and further recommendations will be made at that point. I hope that this section of my webpage has been beneficial. After the dyno testing, I will finish this section, and polish it up a bit so it doesn't sound like the mad ramblings of someone who has nothing better to do than change spark plugs, and race around the neighborhood. For now, please excuse the typos and grammatical errors on this page."


How about that!

 

813KR$, elwood's initial post says he's already read that! "I've read Paul Yaw's recommendations "

Elwood - Go DLIDFIS. It'll only cost you one extra coil, one extra ignitor, plugwires and some time on the forum.

Jeff20b's initial write-up:
http://www.geocities.com/cd23c/dlidfis.html

Installation thread by Moses:
https://www.rx7club.com/showthread.p...hreadid=216618

and I'm sure you'll find other little bits of info about DLIDFIS on the forum and in the archive.

Ignitors can be had from e-bay or from pick-a-part yards, as can coils. If you wanna get some MSD Blaster coils or Diamond, that'll probably help a bit.
Jon

 

Thanks for the kind words.

Bliffle, I could post the text here, but it's kinda long. Just try the link vipernicus posted first.

 

Jeff20B: I read about DLIDFIS on the REPU forum, and it also seems very interesting. One of the things I'm trying to eliminate, however, is igniters. Maybe I've had unusually bad luck, but they've been the most unreliable part of my car for the past 12 years.

Another question I have about DLIDFIS is the effect on engine power. There was a tagline at the bottom of the REPU post on DLIDFIS that indicated an MSD setup produced more power on a dyno.

Also the DLIDFIS post indicates the negative effects of splitting the current by firing two coils with the same MSD box. Does anybody have any evidence that this splitting has a detrimental effect on spark intensity, or is it all speculation?

 

Only one person has tried them both on the dyno, and he didn't change his timing or anything else. I noticed there is a difference in total advance going from stock ignitors to the MSD. The compensation (I think that's what it's called) is set at the factory and is not adjustable. To put it simply, total mechanical advance is off by a few degrees, and can affect engine power output when viewed on a dyno.

Splitting the MSD's already low amperage CD output into two coils will cut that amperage in half. You're feeding your coilS with half as many amps as the MSD normally outputs. My compromise for this is to use an FC leading coil instead because it has only one primary coil to be excited by the MSD, and it's cheaper than buying a new DIS coil.

What if your MSD burned out on you? Your leading ignition would be dead. What if you tried DLIDFIS? If one leading ignitor dies, you can still get home on the other one with leading ignition run through the cap and rotor. I haven't had to use this nice little redundency yet, but I'm glad I have it... just in case. Somebody on the forum has though. I don't remember his name (sorry).

 

FWIW - when we put an MSD 6A on a buddy's GSL-SE autocross car, he called MSD and made sure that it wouldn't have any problem driving multiple coils, as I recall. They told him that there shouldn't be any problem with just 2.
that said, I'm going to try the DLIDFIS, if nothing else because I have a bunch of spare ignitors hanging around, and they never seem to fail...

 

elwood: if you dont like the first gen igniters, get the 2nd gen coil with igniter on it and wire it up Direct Fire style as if the 2nd gen igniter is the msd 6a. Alot cheaper than going all MSD ! ! !

Frankenrex: yea, I also heard of somone calling MSD and they said one MSD 6a could fire a row of coils, with out weakining the out put? just something I have heard?

 

Yeah, it's mentioned in Paul Yaw's article. I guess if he's happy with less amps going to each leading coil, then more power (pun) to him.

His article was written in '98. Mine in '01. A lot of us have learned quite a bit since then. I'm intrigued by the thought of using two FC trailing coils for DLIDIFS. Next time I'm able, I'll grab another so I'll have two to play with.

 

I started out doing Paul suggestions to the tee. But had the same thoughts on the splitting to 2 coils. So now I have a 2nd gen coil with my MSD 6a and a blaster on my trailing, seems like the same out put to me?

 

I started out like that too. I got an MSD 6AL, and already had one more stock Diamond coil (or maybe it was a Bosch stock replacement coil?). I bench tested parallel and series and figured I'd better stick with parallel as per Paul's instructions, even though the amperage would be halved. Probably better than series where the volts would be cut in half.

I just wasn't happy with the performance, and I think my MSD may have a bad relay because it would sort of deisel after shutting it off. Others have mentioned that happening on their MSD setups too. I also adjusted the timing because of the difference in total advance due to the compensation differences in the circuitry of the MSD vs the J-109.

This was a couple years ago. Now that I have an FC leading coil, I'm going to take the MSD plunge again and see if I can get some better results this time around.

By out put, are you refering to the engine power? Or observing the spark jumping in normal atmospheric pressure? Jumping a spark under compression in a running engine requires more power.

Anyway, I'm debating whether to do DLIDFIS or try the MSD again on a freshly rebuilt R5 13B I just installed yesterday. I've got enough components for either one. Hmm...

 

Well, again, I'll say that I think that the MSD puts out much more current than needed to fire the coils. There's only so much you can get out of a coil - I don't think that more trigger current beyond what's required to fire it makes any difference at all.
Oddly enough, this discussion is also going on over in the MegaSquirt Yahoo! group...

Also, I said it in another thread, but I don't think that using two ignitors makes any difference at all, even when firing two coils. Ignitors are just a big switch (transistor) that triggers the coils, same as any other Kettering ignition. As long as it's got the capacity, it should be just as easy to fire two coils as one. Come to think of it, as far as I know (which may not be far enough), the FCs only have one ignitor on the dual leading coil.

Why the hell would you bother with using two FC trailing coils when you already have a purpose made dual-post coil?

Jsut to add to the flames, the only thing that going to direct fire without a CDI box (MSD,etc.) isgains you is bypassing the distributor (not necessarily a trivial thing). Going CDI should theoretically gain you a stronger spark, and an MDS should gain you the multiple sparks per firing event.
Don't mind me, though, I'm still using two coils and a dizzy...

 

Lost my link to Paul Yaw's MSD 6A setup.
Can someone give me the link?
Thanks

 

i think im gonna do this. yeah